Methods, systems, and devices related to a memory system or scheme that includes a first memory device configured for low-energy access operations and a second memory device configured for storing high-density information and operations of the same are described. The memory system may include an array configured for high-density information and may interface with a host via a controller and a cache or another array of a relatively fast memory type. The memory system may support signals communicated according to one or several modulation schemes, including a modulation scheme or schemes that employ two, three, or more voltage levels (e.g., NRZ, PAM4). The memory system may include, e.g., separate channels configured to communicate using different modulation schemes between a host and between memory arrays or memory types within the memory system.